Materials Used in Rapid Prototyping

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Rapid prototyping, also known as additive manufacturing or 3D printing, has become essential for designers and engineers to create prototypes and functional parts quickly and economically. While selecting the appropriate technology is crucial, choosing the material is essential in ensuring the prototype's success. This article will discuss the materials used in rapid prototyping, their properties, and their suitability for different prototyping technologies.

Materials used in CNC Machining

CNC machining is a subtractive process that involves removing material from a solid block to create the desired shape. CNC machines can work with various materials, including metals and plastics. The material choice for CNC machining prototypes is extensive and depends on the customer's requirements. Popular materials for CNC machined prototypes include aluminium, acetal, clear acrylic, mild steel, carbon steel, stainless steel, and brass. However, machining exotic alloys like Inconel, Nimonic, and Hastelloy requires specialist tooling, making it more expensive. CNC machining produces prototypes with excellent surface finishes and isotropic properties, making them ideal for functional parts.

Materials used in 3D Printing

3D printing is an additive process that builds the part layer by layer from a digital file. The material choice for 3D printing prototypes is limited to the materials that the printer can process. Some of the popular 3D printing technologies are Fused Deposition Modelling (FDM), Stereolithography (SLA), and Selective Laser Sintering (SLS), each with its materials.

Fused Deposition Modelling (FDM)

Fused Deposition Modelling (FDM) is one of the most popular 3D printing technologies that use a thermoplastic filament to create the part layer by layer. The material choice for FDM 3D printing is vast, with several manufacturers producing filaments with unique properties. Common materials for FDM prototyping include ABS, PLA, PET, Nylon, and TPU. However, FDM prototyping has some limitations. The parts produced by FDM have anisotropic properties, meaning that the part's mechanical properties depend on the direction of the build. Also, FDM parts may have voids between the layers, affecting the part's mechanical strength.

Stereolithography (SLA)

Stereolithography (SLA) uses a liquid resin that hardens when exposed to ultraviolet light to create the part layer by layer. The material choice for SLA prototyping includes a range of resins with different properties, including ABS-like, PP-like, and PC-like materials. The SLA process produces parts with an isotropic structure and excellent surface finish, making it ideal for creating prototypes with complex geometries.

Selective Laser Sintering (SLS)

Selective Laser Sintering (SLS) uses a laser to melt and fuse powdered material, layer by layer, to create the part. The material choice for SLS prototyping includes various thermoplastics, including Nylon, TPU, and polycarbonate. SLS produces prototypes with isotropic properties and excellent surface finish. SLS is ideal for producing functional prototypes, including parts with snap-fit features, living hinges, and intricate geometries.

Materials used in Vacuum Casting

Vacuum Casting is a rapid prototyping process that produces small to medium-sized production runs of high-quality parts. The process uses a master pattern created using 3D printing, CNC machining, or other techniques, which are used to create a silicone mold. The mold is then filled with a two-part polyurethane resin that hardens to create the part. The material choice for Vacuum Casting includes various urethane-based resins with different properties.

Material choices for vacuum casting prototype parts

Vacuum casting is a cost-effective process for producing small runs of functional prototype parts in a wide range of materials. The parts are cast in a silicone mold, which is made by encapsulating the master pattern of the part in silicone rubber. Once cured, the mold is cut open, and the master pattern is removed. The mold is then assembled, and a measured amount of casting resin is mixed and degassed before being poured into the mold, which is then placed in a vacuum chamber to remove any air that might be trapped in the resin. The mold is then placed in an oven to cure the resin.

The silicone mold is not robust enough for large production runs. Still, it is ideal for prototyping small numbers of parts that require the same functionality as the production part. As with 3D printing, the molded material’s mechanical properties are not identical to those of the production part but are generally very close. The choice of material for vacuum casting is huge, with most resins being two-part systems mixed just before casting. Some materials are also available in color or can be pigmented to match a specific color. Some of the materials we process regularly are polyurethane (PU), epoxy, silicone, polycarbonate (PC), acetal, and ABS.

Material choices for silicone rubber parts

Silicone rubber parts are cast in the same way as vacuum cast parts. Still, they are made using a different material. Silicone rubber is ideal for producing parts used in high-temperature environments, such as molds for casting metals, or in applications where flexibility is important. Silicone rubber can also make parts used in contact with food or drinking water.

Material choices for metal castings Prototype metal castings can be produced using various processes, including sand casting, die casting, gravity die casting, and investment casting. The production process determines the material choice. Still, the metal used for the prototype is usually the same as that used for production. For example, aluminum alloys such as LM25 and LM6 are commonly used for sand castings. In contrast, zinc alloys such as ZL3 and ZL5 are used for die castings. Stainless steel and brass are often used for gravity die castings and stainless steel and titanium for investment castings.

Selecting the right material for prototyping

Choosing the right material for prototyping can be complex. Still, with the right advice and guidance, it need not be daunting. At Prototype Projects, we have years of experience selecting and processing prototype parts materials. We are always happy to help designers make the best project choices.

As a rapid prototyping supplier, we offer various prototyping technologies and materials, including CNC machining, 3D printing, vacuum casting, silicone rubber casting, and metal casting. We hold a wide range of materials in stock for our Express service. We can source almost any material our customers require for prototype parts. We work with a network of specialist subcontractors to process exotic alloys and other specialist materials, managing the work on behalf of our customers to ensure that the finished parts are of the highest quality.

Conclusion

In conclusion, selecting the right material for prototyping is critical to the success of any project. Prototype parts should represent production parts as closely as possible. The choice of material and prototyping technology is crucial in achieving this. We offer a wide range of prototyping technologies and materials at Prototype Projects. We are always happy to help our customers select the right material for their projects. With our expertise and experience, our customers can be confident that their prototype parts will meet their needs and exceed their expectations.

Reprinted from Good Tech - “Materials Used in Rapid Prototyping”